With the continuous development of the Thin Film Transistor Liquid Crystal Display (TFT-LCD) technology, the LCD manufacturers are in pursuit of the lowest cost and the maximum production efficiency continually. The cost of the module material occupies about 50% of the total cost of the LCD material, thus reducing the material cost of the module has direct significance to the reduction of the whole cost. Whereas the significance of the fine pitch technology lies in favor of reducing the electrode pitch, reducing the production cost and increasing the pressing efficiency, so as to maximize the capacity of production; therefore, further improving the fine pitch technological capacity becomes a long-term target pursued by many LCD vendors.
FIG. 1 is a structural schematic view of a connecting structure by pressing of an array substrate and a flexible circuit board in the prior art. As shown in FIG. 1 , the array substrate comprises a first substrate 101 and a plurality of first electrodes 102 arranged on the first substrate 101; the flexible circuit board comprises a second substrate 103 and second electrodes 104 arranged on the surface of the second substrate 103; the first electrodes 102 and the second electrodes 104 are electrically connected through Anisotropic Conductive Films (ACF). The ACF comprises two primary substances, respectively conducting particles 105 and thermosetting resins. The first electrodes 102 and the second electrodes 104 are connected together through the conducting particles 105 by means of the pressing process, so as to realize circuit conduction, wherein the thermosetting resins play the function of physical connection and ensure connection intensity.
With the development of the liquid crystal panel towards the direction of high resolution, the number of leads on the array substrate increases correspondingly. If the electrode pitch (which refers to the distance between the same positions of two adjacent first electrodes 102) is not shortened, the area of the array substrate will be increased, and the cost will also be increased correspondingly, this is unfavorable for control of the production cost, so it becomes very important to shorten the electrode pitch and optimize the fine pitch.
In the connecting structure by pressing of the array substrate and the flexible circuit board, Pitch=W+G+2M, wherein M represents the offset, which refers to the offset of the center of the first electrode 102 and the center of the corresponding second electrode 104, the offset is caused by the accuracy problem of pressing apparatus, which cannot be avoided and can only be reduced as much as possible; G represents the minimum insulating distance, which refers to the minimum distance allowed between the first electrode 102 and the next second electrode 104 of the flexible circuit board, i.e., the minimum distance set for ensuring no short circuit between two adjacent electrodes, the minimum insulating distance is related to the size and density of the conducting particles within the ACF, the larger the conducting particles and the higher the density is (i.e., the better the conductivity is), the larger the minimum insulating distance will be required, vice versa, the minimum insulating distance will be smaller, while the fine pitch requires the minimum insulating distance the smaller the better; W represents the minimum pressing width, which refers to the minimum overlapping width of the first electrode 102 and the second electrode 104 required for ensuring conduction and stability of the circuit. The minimum pressing width is related to the density of the conducting particles, the larger the density of the conducting particles is, and the larger the number of conducting particles within the unit area is, the larger the conducting area is (the better the conductivity is), thus the overlapping width can be shortened, the minimum pressing width will be small, which is a result desired by the fine pitch. However, the minimum insulating distance requires a relatively small density of the conducting particles, while the minimum pressing width requires increase of the density of the conducting particles, the two cannot be met simultaneously, so the fine pitch optimization level in the current industry still cannot further reduce the pitch between respective electrodes effectively.